1. Field
The present disclosure relates generally to power converters and, more specifically, to feedback circuits for power converters.
2. Description of Related Art
Electronic devices are typically used with power conversion circuits. Switched mode power converters are commonly used due to their high efficiency, small size and low weight to power many of today's electronics. Conventional wall sockets provide a high voltage alternating current (ac). In a switched mode power converter, a high voltage ac input is converted to provide a well-regulated direct current (dc) output. In operation, a switch, included in the switched mode power converter, is utilized to control the desired output by varying the duty ratio (typically the ratio of the on time of the switch to the total switching period) and/or varying the switching frequency (the number of switching events per unit time). More specifically, a switched mode power converter controller may determine the duty ratio and/or switching frequency of the switch in response to a measured input and a measured output.
Conventional power converters include a controller that may be configured to provide a regulated voltage and/or a regulated current at the output of the power converter. In general, a regulated power converter may also be referred to as a power supply. One type of conventional controller monitors a voltage at the output of the power converter in order to provide a regulated output voltage while another type of controller monitors a current at the output in order to provide a regulated output current. One way to measure the output current is to include a sense resistor at the output of the power converter such that the output current flows through the sense resistor and the resultant voltage dropped across the sense resistor is proportional to the output current. However, the voltage dropped across the sense resistor is typically large and often referenced to a voltage level different than that of the power converter controller. Thus, additional circuitry, such as an opto-coupler or a bias winding, is often needed to level shift the voltage across the sense resistor in order to interface with the controller. However, these components can be bulky and expensive.
Additionally, for some conventional applications, the input of the power converter may be galvanically isolated from the output of the power converter. In general, galvanic isolation prevents dc current from flowing between the input and the output of the power converter Implementing galvanic isolation, however, usually requires additional circuitry, such as a magnetic coupler or an opto-coupler, which adds cost to the power converter.